WASHINGTON (Reuters) - The White House threatened to veto legislation on Wednesday that would bar CIA contractors from interrogating suspected terrorists, in the latest debate over treatment of detainees in the U.S.-declared war on terrorism.

The White House issued the threat in a notice to Congress as the Democratic-controlled House of Representatives began considering a broad measure to authorize funding of U.S. intelligence activities for the 2009 fiscal year.

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The bill contains many provisions "that conflict with the conduct of intelligence activities," the White House budget office told Congress. "If (the bill) were presented to the president, the president's senior advisors would recommend that he veto the bill."

The contractor provision was the first objection listed by the White House.

CIA Director Michael Hayden has acknowledged that outside contractors were used to conduct some interrogations in the agency's detention program for suspected terrorists, which has been widely condemned for harsh techniques that critics say amount to torture.

He told Congress in February he believed contractors helped conduct "waterboarding," the fiercely condemned simulated drowning technique that he acknowledged using on three al Qaeda suspects.

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But the White House said prohibiting contract interrogators could deprive the program of necessary questioning skills and expertise.

"Such a provision would unduly limit the United States' ability to obtain intelligence needed to protect Americans from attack," it said.